The prior art includes several devices that utilize well known methods of applying tension to a strapping band. In one such design, one end of a band is held between stationary and moving toothed gripper plates. The moving gripper contacts a first end of the band with all its teeth simultaneously under the influence of a previously charged spring. An operator applies force to a tension handle of a tension mechanism that includes a windless. The windlass rotates and tightens a second end of the band threaded through one of its slots. When the pulling force is applied, a moving gripper plate acts as a force resolution wedge that increases a normal component of the pressing force so that the band is sufficiently held between the two plates. The efficiency of holding increases proportionally with an increase of the pulling force.
It is necessary in the current art designs to have a very strong spring in the mechanism and extremely sharp teeth on both the stationary and the moving plates in order to hold a heavy duty polyester band. The heavy duty polyester band, in contrast with a traditional polypropylene strap, has a hard and slick surface. At the end of each working cycle, when the apparatus is moved away from the band and a new band has not yet been loaded, the sharp teeth of the moving gripper plate (made from heat treated steel) are forced by the spring to strike against the sharp teeth of the stationary gripper plate (also made from heat treated steel). As a result of this interaction, all the teeth eventually lose their sharpness, and therewith their ability to prevent a band from slipping between them. This commonly used mechanism design is described in U.S. Pat. No. 5,181,546 to Synec, issued Jan. 26, 1993, and U.S. Pat. No. 4,056,128 to Konrad, issued Nov. 1, 1977.
Accordingly, it is an object of the present invention to provide a banding device that functions without the teeth of the moving gripper plate striking those of the stationary gripper plate.
It is a further object of the present invention to provide a device that returns the windlass automatically to an optimal loading position.